Flexion Therapeutics (Burlington, MA) has announced1 the publication of its Phase 3 trial results2 of ZILRETTA, a triamcinolone acetonide extended-release intra-articular (IA) injection for the management of knee osteoarthritis (OA). FDA approved the non-opioid medication in October 2017,3 and data from this pivotal trial served as the foundation for its NDA approval.

The randomized, double blind, placebo-controlled trial2 enrolled 484 patients at 37 centers worldwide. Patients were randomized to one of three treatment groups: a single IA injection of ZILRETTA (32 mg), normal saline-placebo, and triamcinolone acetonide in crystalline suspension (TAcs, 40 mg). The primary study objective was to assess the magnitude of pain relief in patients receiving ZILRETTA at 12 weeks, compared with saline-placebo, as measured by the weekly mean of the average daily pain (ADP) score.

Each patient was evaluated for efficacy and safety during seven outpatient visits over 24 weeks after receiving an injection. Overall, ZILRETTA met its primary endpoint, demonstrating a highly statistically significant (P < 0.0001) reduction in average daily pain (ADP) versus saline-placebo at week 12 (approximately 50% reduction in pain from baseline over Weeks 1 through 12), with durable pain relief in patients with moderate to severe OA knee pain.

Other key findings include:

ZILRETTA was favored by trial subjects when compared with saline-placebo and TAcs at each time point through 12 weeks on exploratory measures — WOMAC A1 (pain), WOMAC B (stiffness) and WOMAC C (function) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) quality of life subscale.

Adverse events were reported as being generally mild and occurring at similar frequencies across treatment groups. The most common adverse events were joint pain, headache, and back pain.

“These data reflect the clinical trial rigor necessary to guide the understanding of this novel therapeutic option and represent an important milestone for the OA scientific and clinical communities,” Philip Conaghan, MD, PhD, lead study investigator and chair of Musculoskeletal Medicine at the University of Leeds, said in the company’s release.

Update 4/27/18: Flexion has announced updated results from the clinical trial evaluating repeat administration of ZILRETTA at the Osteoarthritis Research Society International World Congress. Click here to learn more.

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